Field of the Invention
The present invention relates to a secondary battery.
Description of Related Art
Alkaline secondary batteries and nonaqueous electrolyte secondary batteries are used as power supplies for driving electric vehicles (EVs) and hybrid electric vehicles (HEVs, PHEVs) and in stationary storage battery systems for suppressing the variation in output power of photovoltaic generation, wind power generation, and the like, and for peak shifts in system power in order to store electric power during the night time and to use the electric power during daytime.
A battery used for such a purpose is provided not only with a gas release valve that releases internal pressure when the pressure in the battery outer packaging increases but also with a current breaking mechanism that breaks the electrical connection between an external terminal and an electrode assembly inside the outer packaging as shown, for example, in Japanese Published Unexamined Patent Application No. 2013-157099 (Patent Document 1).
In the art disclosed in Patent Document 1, in a positive electrode collector or a negative electrode collector that makes up a current breaking mechanism, and a second insulating member, a first opening, a second opening, and at least one third opening or cutout formed in the positive electrode collector or the negative electrode collector, and protrusions formed on the second insulating member are engaged with each other.
In Patent Document 1, the second insulating member and a lower first insulating member are engaged with and fixed to each other in a latching manner.
The second insulating member can be made of a softer resin material. For example, when the second insulating member is made of a softer resin material, the damage or breakage of the second insulating member can be prevented when connecting the second insulating member and the lower first insulating member. However, the inventors found that, when the second insulating member is soft, there is the following new problem.
The positive electrode collector or the negative electrode collector is connected to an inversion plate. The positive electrode collector is connected to a positive electrode plate, and the negative electrode collector is connected to a negative electrode plate. A fixing portion in which the positive electrode collector or the negative electrode collector and the second insulating member are fixed is provided. For this reason, the weight of the electrode assembly including the positive electrode plate and the negative electrode plate is applied to the second insulating member through the positive electrode collector or the negative electrode collector.
The second insulating member is connected to the lower first insulating member, and is supported on the sealing body side. The fixing portion in which the positive electrode collector or the negative electrode collector and the second insulating member are fixed is located nearer to the connection portion between the positive electrode collector or the negative electrode collector and the inversion plate than the connection portion between the second insulating member and the lower first insulating member. Therefore, when the second insulating member is made of a soft material, the second insulating member may deformed by the weight of the electrode assembly. When the second insulating member is deformed, the state of the connection portion between the positive electrode collector or the negative electrode collector and the inversion plate changes, and therefore a phenomenon occurs in which the current breaking mechanism does not operate normally.
Such a problem can arise not only when the second insulating member is made of a soft resin material but also when the second insulating member has a small thickness or when the weight of the electrode assembly is very great.